05. Context Managers in Depth

Context managers simplify resource management (files, network connections, etc.). They ensure proper setup and cleanup.

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The with Statement

with open("example.txt", "w") as f:
    f.write("Hello, world!")
# File is automatically closed

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How It Works

A context manager implements two methods:

• __enter__: Setup
• __exit__: Cleanup

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Creating Your Own Context Manager

class ManagedResource:
    def __enter__(self):
        print("Acquiring resource")
        return self
    def __exit__(self, exc_type, exc_value, traceback):
        print("Releasing resource")

with ManagedResource():
    print("Using resource")

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Contextlib Helpers

from contextlib import contextmanager

@contextmanager
def simple_cm():
    print("Start")
    yield
    print("End")

with simple_cm():
    print("Inside")

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Practice Challenge

Write a context manager that measures and prints how long a block of code takes to run.

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Wrap-Up

• Use with for safe resource management.
• Create custom context managers with __enter__ and __exit__.
• Use contextlib.contextmanager for simpler cases.